The performance of power devices such as power inductors and power FETs (Field Effect Transistors) affects the performance of switching power converter applications. The power inductor is one of the largest and most lossy components in a switching power converter, and it is accountable for much of the weight and the size of switching power converters. Several figures of merit are considered for power inductors including the inductance density, the current/power density, the DC resistance, the AC characteristics and the saturation current. In order to obtain higher inductance density, in other words, achieving the required inductance in as small area as possible, technologies like planner inductor, integrated inductors, micro-fabricated inductor and on chip inductor have emerged over the years. Saturation current is related to the core structure as well as the magnetic core material. For a given core structure and design, employing a magnetic material with higher saturation flux density helps to obtain a higher saturation current.
The power inductor, as a form of multiple winding coupled magnetic structures, has been used in many applications, such as is in multi-phase power converters. One of the main advantages of the coupled power inductor used in DC-DC power converters is the ability to obtain smaller equivalent transient inductance (advantageous for lower output voltage dynamic deviation under transients) with a larger equivalent steady-state inductance (advantageous for smaller steady-state output voltage ripple and higher power efficiency).
In a two-phase inductor, the two inductor windings can be directly or inversely coupled. Inversely coupled power inductor was employed in the multi-phase switching power converters to improve both the steady-state and transient performances. Permanent magnet power inductors (PMPI) utilize a permanent magnet (PM) to partially offset the flux in the magnetic core due to the DC component of the winding current, so that a higher saturation current could be obtained by the same core structure power inductor.